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Shoemaker by David Levy, Princeton University Press, $24.95, ISBN
0691002258

IN July 1994 Gene Shoemaker saw something that he never dreamed he’d see: a
comet smash into a planet. Thankfully, Comet Shoemaker-Levy 9 collided with
Jupiter, not Earth. But it confirmed something Shoemaker had long suspected:
extraterrestrial impacts are a regular occurrence and have been as much a force
in shaping the terrestrial landscape as the slow creep of oceans or the
weathering of mountains.

Such a view was heresy in 1952, when Shoemaker first visited Meteor Crater in
Arizona, the 50,000-year-old scar of a gargantuan impact. The 24-year-old
American geologist was struck by the similarity between the spectacular
1.2-kilometre basin and craters made by nuclear explosions. A later discovery
clinched the case—”shocked” minerals forged at temperatures and pressures
greater than existed in any known lava flows.

Shoemaker went on to discover dozens of previously unsuspected craters all
over the world. He also looked at the Moon. Its unweathered surface is a
pristine record of the bombardment of the Earth-Moon system over the past 4.6
billion years.

Shoemaker worked on the Ranger lunar probes, then Surveyor, and finally
Apollo. His ambition had been to be the first geologist on the Moon. But a rare
brain disease that gave him occasional blackouts ruled him out as a pilot, and
by 1965 it had dashed his hopes of being an astronaut.

He went on to do the next best thing: he trained the Apollo astronauts to be
geologists, a task he tackled with his customary energy and enthusiasm. But his
was a lone voice badgering NASA into taking science seriously. Eventually he
became disillusioned, and left the Apollo programme when it became clear that
science was a very low priority.

David Levy, co-discoverer of Comet Shoemaker-Levy 9, tells the story of
Shoemaker’s scientific odyssey with wit and panache. He shows insight into the
man too. We learn of Shoemaker’s inability to complete a project before plunging
enthusiastically into the next, more exciting one. It was a habit that would
have sunk most scientific careers, but in his case it made for extraordinarily
wide-ranging discoveries.

We also learn of Shoemaker’s lack of interest in his three children when they
were young: “He was not a baby person or small child person, he wanted someone
to talk to.” It was clear to his children that he put his science first and that
they came a poor second. In fact, reveals Levy, they came third—after
Shoemaker’s wife Carolyn.

Bored when her children had left home, and keen to spend more time with her
often-absent husband, Carolyn gave up her job as a florist and embarked with him
on a project to find the comets and asteroids that were causing the craters he
had found. Nobody could have guessed how
successful she would be. By 1987, she had smashed the 200-year-old record for
cometary discoveries, oddly enough held by a near namesake—Caroline
Herschel, sister of the discoverer of Uranus.

But the most famous cometary discovery was, of course, Shoemaker-Levy 9. The
world had a ringside seat as its 20-odd fragments hit Jupiter’s atmosphere with
the explosive power of thousands of full-scale nuclear wars. “Now what are the
odds to have such a rare event happen in the decade that all the new infrared
detectors became available, as the Galileo spacecraft was in position to see the
hits directly, and only six months after the Hubble was fully operational?”
asked Shoemaker. “Folks, we had a bloody miracle.”

Shoemaker died in a car crash in Australia in 1997. But this was not the end
for “the greatest planetary scientist of the century”. The story of his life has
an almost mythic closure to it. Early in 1999, Shoemaker’s ashes, carried by
Lunar Prospector, landed in the lunar dust. The man who had for so long dreamed
of going to the Moon finally got his wish.